Everyone knows that in order to breed, fish need to spawn. However, for some, viviparous species are a discovery. In general, fish breeding is a long and complex process that every aquarist must learn. Everything is in order in this article. Proper fish care is the backbone of fishkeeping.
Reproductive system of fish
Most of the species of fish that exist on earth are represented by two sexes. The sex glands in females are the ovaries: eggs are formed in them, which are usually called eggs. Ripe eggs are hatched through short canals that open into the cloaca or genital opening. Some species of cyclostome fish do not have such ducts, so the eggs enter the cavity, then through the urogenital opening.
The reproductive system of male fish is supplied with paired milk or testes: spermatozoa mature in them. Often there is a special channel for their removal, but sometimes it is combined with the urethra.
Development stages of fish
Considering the entire life path, the development of fish can be divided into six stages:
- Embryonic (germinal). During the period of formation in the egg, the future fry feeds in an endogenous way. Until the moment when the embryo is formed and prepares for “hatching”, it feeds on the yolk from the yolk sac.
- Larval. The future fish switches to external nutrition: first mixed, then completely exogenous – microscopic algae and ciliates. However, the organism is just beginning to form, so clear larval signs remain.
- Fry. The third stage of development is characterized primarily by the fact that the fry acquires the features of an adult fish. So, an unpaired fin fold is transformed into fins, and small scales begin to appear on the body. At the same time, sexual differentiation begins, but the genitals themselves are still undeveloped. The diet is replenished with larger foods such as crustaceans and insect larvae.
- Juvenile. In adolescence, the sex glands are finally formed, secondary signs begin to develop (color, fin length, etc.), if any of the species.
- Adult. The fish reaches puberty, and by this time it has all the signs of a formed organism. The specimen is ready for breeding.
- Senile. Like any organism, the life cycle of fish sooner or later comes to an end. Over time, they lose the ability to leave offspring. At the same time, growth slows down or completely stops.
The development of fish can be direct or indirect. In the first case, the fry are born similar to adults in external and internal structure, and differ only in size. This is usually inherent in viviparous. Indirect development occurs in spawning animals, when a larva is formed from the embryo, and only then a fry.
how are fish fertilized?
Reproduction of bony fish, depending on the species and habitat conditions, occurs in different ways and at different ages. The most common is sexual, but some aquatic vertebrates are characterized by parthenogenesis and gynogenesis. Despite the fact that mainly fish are dioecious animals, they have the phenomenon of hermaphroditism.
This type is typical for those who have individuals of both sexes, that is, for the majority. The fertilization of fish itself can proceed in different ways and be:
- Internal. Then the male fertilizes the eggs inside the body of the female, and only then spawning occurs. This method is used by guppies, swordtails, mosquitoes and others.
- Outside. This method is found in most species. The male produces insemination after the eggs have left the female – in the water.
Parthenogenesis in fish is a method of reproduction and development, in which eggs do not require fertilization by a male. Nevertheless, it belongs to the sexual cells, since the development of future fish takes place in the reproductive cell of the female.
Embryos in non-seeded eggs develop to larvae, most of which die while eating the yolk. Sometimes no one comes out of the eggs at all. Parthenogenesis is ineffective, and therefore a rare method, characteristic only of herring, salmonids, cyprinids and sturgeons.
One of the varieties of the previous breeding method is called gynogenesis. Here, too, the process of fertilization by the male of this species is not observed, but other fish are involved in this.
After throwing, the development of embryos in the eggs is stimulated by the spermatozoa of males of related species. For example, the future offspring of goldfish appears thanks to the milk of carp or roach. They enter the cell, but their nuclei do not fuse.
This is interesting: only female fry appear during gynogenesis.
Hermaphrodite is a fish in which both female and male reproductive systems are present. Both eggs and sperm develop in them, but the individual cannot fertilize itself: these two components mature in turn.
Let’s take an example with a red pagell. Throughout life, individuals change sex once: in the first years they are females, with age, male characters become dominant. Other species have experienced similar changes several times. Some herring, salmon, perch, and carp species have a tendency to hermaphroditism.
Attention: aquarium fish, mainly viviparous, also have sex change. A pointed anal fin speaks of the reincarnation of a female guppy into a male. The sword bearers grow a sword on their tail. Reverse phenomena are less common.
How do fish breed?
The breeding process of wild species is called spawning. The instinct for this develops together with the reproductive cells, and then individuals migrate to a place with the most favorable conditions for breeding offspring. This happens most often in the spring.
The overwhelming majority of fish spawn, and the embryos in it form when the clutch is in the water. Most often, after the fertilization process, parents leave eggs, and some even begin to eat it. Another part of the eggs remains without insemination, and the “hatched” fry often die before they reach the sexually mature period.
However, fish care for the offspring exists: some protect eggs, as well as those born at the larva and fry stages. There are several spawning models for this.
Scattering of eggs
For such fish, the absence of parental instincts is characteristic. Individuals of the female sex “scatter” eggs in random places, after which they settle on the ground, stones, vegetation and other surfaces. This is what some of the carp, haracin and other fish do.
Note: For ornamental fish with a scattering pattern, a separate spawning aquarium must be created. The ground is small glass beads covered with a fine mesh. This will protect the eggs from being eaten by adults.
Masonry formation in the water column
This model involves laying out a large number of small light eggs without shelter anywhere. So caviar is quickly fertilized, and subsequently carried by the current – if we talk about wild species.
As for ornamental fish, it is almost impossible to get offspring from them in a general aquarium: they quickly eat eggs. Ideally, males and females should be kept separate for each other, only during the breeding season, transplanting them into a separate aquarium. After spawning, the parents are moved out. This applies to red neons, barbs, labeos, bocii and some haracinths.
Masonry formation in caves and gorges
Some fish live in an aggressive environment, so they tend to hide the eggs. Some females immediately after hatching collect eggs in their mouths and keep them there until the fry hatch. Others are looking for the most secluded place in the form of driftwood, caves, shells. As for aquariums, such conditions are mandatory for the reproduction of parrots, Julidochromis, scalar, discus.
Immersion of eggs in the ground
This method is typical for fish living in shallow water bodies with muddy bottoms. The caviar swept into the substrate is preserved even if the reservoir dries up for more than a month. As soon as the rains come and it fills up again, a new generation of fish will be born.
This is interesting: Killi owners can store their eggs in a dry place for a couple of months, or even mail them to other aquarists.
Surprisingly, labyrinth fish such as gourami and cockerels keep their mate throughout their lives. During the mating season, the male builds a nest on the surface of plants and other small particles, holding the material together with foam. A little later, the female will lay eggs here and will guard it until the fry appear.
Mating of viviparous fish does not require any special conditions or season. They often spawn several times a year. The only thing is that too high a water temperature can lead to premature birth and, as a result, to the appearance of non-viable fry.
Attention: offspring must be kept separate from adults, otherwise the fry may be eaten.
Viviparous aquarium fish include species such as
- priapellas and others.
In the wild, katrans and some shark species are ovoviviparous. Their feature is the gestation of eggs in the body first, then fry until they are fully formed. Among the aquarium inhabitants, these are the South American river stingray and leopoldi, but these species are recommended only for professionals.
Fish Breeding classification
An important role in spawning is played not only by the season, which awakens the instincts, but also the conditions. In this regard, the researchers identified several groups, individuals in which one or another environmental factor unites.
According to S.G. Kryzhanovsky
According to the theory of Doctor of Biological Sciences Sergei Grigorievich Kryzhanovsky, fish are divided into five ecological groups:
- Lithophiles. They prefer rivers with currents and stony ground, occasionally oligotrophic lakes and coastal areas. This includes sturgeon and salmon, as well as whitefish, podust and barbel.
- Phytophils. These fish like stagnant bodies of water or rivers with very slow currents, as well as a large amount of underwater vegetation. It is on the plants that pike, bream, crucian carp, tench, roach and others spawn.
- Psammophiles. They spawn in reservoirs with a sandy bottom with sparse vegetation. The scientist attributed to this group minnows, loaches, spikes.
- Pelagophiles. They are found in rivers and lakes, where they spawn in the water column. The main species are herring, sabrefish, silver carp, cod, grass carp.
- Ostrakophiles. Used as a “nest” shells of bivalve mollusks and even crab shells. This parasitism is engaged in by bitterness.
According to E.K. Balonu
Another scientist, E.K. Balon:
- Not guarding:
- Spawning without substrate and on substrate. These include fish that lay floating eggs, spawning on rocks, underwater vegetation, on sand (including on land in a humid environment), as well as on polychaete tubes and on gravel with pelagic larvae.
- Hiding their offspring. These species can also spawn on sand, rocks, gravel, as well as in depressions, grottoes, crevices, on live invertebrates and in humid environments in the tidal zone. Some fish eggs can survive without water.
- Forming masonry on the substrate. In this case, fish can spawn in almost all conditions – on the surface of the water, stones and plants.
- Building nests. Some parents, before spawning, equip a place for incubation of future offspring. The materials are foam, substrate, stones, gravel, plants, sand and so on.
- Carrying outwardly. Such fish transfer clutch in body cavities or on top of it, sometimes hatching on auxiliary organs. Some individuals are able to keep eggs and fry in their mouths, gills or a special brood chamber.
- Embroidering internally. This includes species with internal fertilization and viviparous.
how to breed aquarium fish at home?
It is worth dwelling in more detail on the features of breeding ornamental fish, as well as questions and difficulties that an aquarist may face.
The timing of puberty
In different aquarium fish, sexual maturity occurs at different times, and these fluctuations are also characteristic within the same species. For example, guppies and males are capable of breeding as early as 3-5 months, and males mature earlier. Burbus need a little more time – 6-8 months, scalars – from 8 to 12 months. In general, small species mature much earlier than large ones.
When do fish spawn?
The conditions for spawning fish in nature are suitable temperature conditions and the availability of a food base. Since all this in an artificial environment is regulated by a person, you can induce the desire to have offspring at any time of the year. Of course, many aquarists know that the captive breeding season is still in the spring or fall, but this also depends on the feed obtained from the water.
How to determine readiness for breeding?
First of all, the readiness of the fish is determined by age: it is possible to plant a pair for spawning and fertilization of the clutch when they reach maturity. It is important to observe the cyclical nature of this process and to plant the female with the male in the spawning aquarium every month – so her health will be safe.
Games can be a sign of the beginning of the mating season. For example, cleaning pebbles or leaves in cichlids, building a nest in labyrinths, and so on.
Important: if you miss the moment of spawning and do not plant the pair in suitable conditions for more than a month, most likely the female will no longer be able to spawn.
Stimulation to reproduce
You can motivate fish to breed offspring in various ways that change the environment or the amount of vitamins and minerals in the individual’s body. Basic ways:
- Plentiful and varied food (in particular with a large amount of protein and nutrients);
- Fresh water (this way more oxygen appears in the aquarium);
- Change in water temperature (increase by several degrees);
- Adding alder cones, oak bark, peat infusion (so the transparency of water and its chemical composition will approach natural indicators);
- Substrates and secluded places that serve as spawning grounds for certain species;
- Lighting (an increase in daylight hours increases the chance of spawning);
- The water level in the spawning ground (about 8-15 centimeters is suitable for small fish);
- Chemical stimulants containing hormones;
How do fish mate?
Ornamental species are either spawning or viviparous fish. Most often, eggs are fertilized already in water: this can be a haphazard approach, but sometimes, in order to cover as many eggs as possible, the male presses against the female, hugging her fins. A viviparous female is fertilized internally by a male individual: he injects the seed through the gonopodium – the anal fin in the form of a tube. Spermatozoa enter the female in portions – in some bags that dissolve inside within 10 minutes.
Signs of pregnancy in a female fish
In viviparous women, the main indicator is the convex abdomen of the female. On average, it grows from 20 to 40 days. The belly can be rounded or more square.
Important: Sometimes pregnant females can be confused with overfed males if the species does not have sexual dimorphism. To check who is in front of you, it is enough not to feed the fish for a couple of days.
Sometimes a pregnant female will develop a dark or bright red spot on the back of the abdomen. As pregnancy progresses, it becomes more and more noticeable. However, some fish always have this speck.
Here if you want to know if your fish is pregnant or not.
When to transfer a female for childbirth
In addition to a huge abdomen and a noticeable “pregnancy spot”, swelling of the anus testifies to the imminent onset of labor. As a rule, the fish gives birth 1-2 days after the appearance of this symptom. The behavior of the female also changes: she always wants to hide, often freezes in place – then wait for the fry in 1-2 hours. It is advisable to plant the expectant mother in a separate aquarium, comfortable for breeding, until this moment.
Most of the viviparous can give birth in a common aquarium, but most likely the fry will be eaten by its inhabitants. The same applies to spawning fish. To prevent this from happening, it is necessary to prepare a separate aquarium with the conditions necessary for a particular species.
If it is not possible to organize a separate place for the female, you can use a trap – a plastic chamber with a double bottom. A giving birth female must be placed in it so that the babies are born safely. After giving birth, the female is returned to the main aquarium, and the fry are planted in a separate, perhaps a small tank.
Number of offspring
How many fry will be born in a viviparous fish depends on many factors: species, age, health status, pregnancy, habitat and spawning conditions. A young guppy gives on average 8-10 fry, older ones – up to 20-40, some – up to 100 pieces. A brood of swordsmen can reach 200 individuals. In the petsilia – from 20 to 50 fry.
After giving birth, the female must be quickly transplanted into a common aquarium, since many are prone to eating their own offspring. If you are not sure that the birth is over, you can temporarily transplant the female into another container or trap for a couple of hours.
In general, aquarium fish recover quickly after a live birth: a healthy female will show activity and appetite. If lethargy or unusual behavior is noticeable, it is necessary to consult a specialist.
Relocation of fry to a common aquarium
Even under equal conditions, fry can develop at different rates, so often the issue of resettlement has to be decided individually, “by eye”. Brave aquarists release juveniles after 10-14 days, others – no less than a month later.
The main reference point is the size of the fish: if it is large enough that an adult cannot eat it, then you can move the fry to a common aquarium.
Attention: fish from the same litter can also vary in size, and sometimes the larger ones start eating the smaller ones. To prevent this, you need to plant them in different containers.
Breeding features of popular fish
|Scalar||The optimum temperature during the spawning period is 27 degrees. Protein feed stimulates the fish best. One female is capable of spawning 800 eggs at a time.|
|Cockerel||Fertilization of eggs occurs in water: the male first helps the female to sweep them by pressing on her fins, then releases milk. The caviar is in a nest of bubbles.|
|Neon||The main conditions for spawning are soft water and diffused light. The female lays up to 200 eggs, of which fish larvae appear in 1.5 days.|
|Swordsman||Fish with high fertility: can give birth to 200 fry per month. The presence of dense vegetation in the aquarium is imperative.|
|goldfish||Reaches sexual maturity only by 2-4 years. The spawner should simulate a stranded area of no more than 20 centimeters. Under such conditions, the female lays up to 3,000 eggs. Several males are needed for fertilization.|
|Danio||Requires a layer of soil of at least 3 centimeters and a net on it, as well as plants with a long stem.|
|Guppy||The most unpretentious in terms of reproduction. The only condition is the presence of vegetation in the spawning grounds.|
Problems associated with breeding fish
Sometimes it is difficult for novice aquarists to cope with breeding even the most unpretentious fish. This issue must be approached responsibly, to study the biological nuances of a particular species. What problems owners may face:
- Inappropriate aquarium volume. The appearance of offspring can lead to crowding, and, as a result, stress, aggression and poor health.
- The fry die. This could be due to an inappropriate diet or poor water quality.
- Degeneration of the population. Sometimes, due to closely related relationships, fish have weaker, faded offspring. To prevent this from happening, you need to separate the offspring of different sexes.
- Females do not fly. It is necessary to check the parameters of the water in terms of temperature and softness. If the problem is not in the conditions, then you can try to change the male.
In matters of breeding ornamental fish, the most useful thing is the real experience of other aquarists. Who do you breed at home and how successful is it? Share your stories in the comments.